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534                       CHARACTERS OF PRIMATES                       CHAP,
group to which so many others appear to converge. It is dis-
puted, for example, whether the Chiiacidae among extinct Lemurs
are rightly placed, or whether they should be referred to the
Creodonta. The number of primitive characters seen among the
Primates, even In Man himself, is remarkable. Of these the more
important are the five digits of both limbs arid the plantigrade
walk, the presence of clavicles and of a centrale, and the absence
of a third trochaiiter. All these features distinguish the early
Eutheria.
SUB-ORDER  1.    LEMIIHOIDEA.1
The animals known as Lemurs, from their nocturnal and ghostly
habits, are on a lower level of organisation than the other division
of the Primates. Even the external form enables the members
of the present sub-order to be readily distinguished from the
higher Anthropoidea. The head is more like that of a Pox, with
a sharp muzzle; it lacks the human expression of the face of even
the lower among the Apes. The long tail is never prehensile, and
there is never any trace of cheek pouches or of integumental
callosities, which are frequently so characteristic of the Apes.
The Lemurs agree with the remainder of the Primates in having
pectoral mammae (sometimes abdominal ones are present in
addition, and in Hapalemwr---in  the   male at  least---there is  a
mamma upon each shoulder), in having opposable thumbs and
toes, and in the flattened digits. The tail varies from complete
absence (in the Loris) to a great length and bushiness in
the Aye-aye. The pectoral limbs are always shorter than
the hind-limbs; the reverse Is occasionally the case in the
Anthropoidea. A curious contrast between the two divisions
of the Primates concerns the digits of the hands arid feet. In
the Anthropoidea it Is the hallux or pollex -which is subject to
great variation. In the Lemurs, on the contrary, the thumb
and great toe are always well developed, but the second or
the third digit constantly shows some abnormality; thus the
singular elongation of the third digit of the hand in Chiromys
and the absence of .the index in the Potto.2 In all Lemurs the
1 See Dr. Hivart's papers in Proc. Zool. Soc.  1864,  -65, -66,  -67,  and -73  for
osteology and teeth.
a Mime an<l Mivart,  Trans. Zool. Soc. vii. 1869, p. 1.